NASA's Opportunity rover has found another spot where warm water may have flowed or percolated on Mars long ago, researchers announced Thursday.

Opportunity made the find while studying a rock on the rim of Mars' huge Endeavour Crater. The rock, called Tisdale 2, has unusually high levels of zinc and bromine, elements often deposited by water — especially hot water. The rock is unlike anything else ever seen up close on Mars, researchers said.

On Earth, life just needs water and energy to get a foothold, and hydrothermal systems teem with microbes. Such sites are thus good places to look for evidence of ancient life on Mars, which is cold and dry today.

Science editor Alan Boyle's blog: "Astronaut Abby" is at the controls of a social-media machine that is launching the 15-year-old from Minnesota to Kazakhstan this month for the liftoff of the International Space Station's next crew.

Opportunity's twin rover, Spirit, discovered strong evidence of an ancient hydrothermal system near its landing site back in 2007. While researchers are still interpreting Opportunity's data, they think Endeavour's rim might well harbor another one. [Mars Photos by Spirit and Opportunity]

"When you find rocks on Earth that are rich in zinc, they typically formed in a place where you had some kind of hydrothermal activity going on," Steve Squyres of Cornell University, principal investigator for Spirit and Opportunity's mission, told reporters Thursday. "This is a clue that we may be dealing with a hydrothermal system here."

A cradle for life?
Endeavour is a giant impact crater about 14 miles (22 kilometers) across. Opportunity just arrived at its rim on Aug. 9, at a site called "Cape York." The region looks completely different from other parts of Mars that Spirit and Opportunity have explored, researchers said.

Tisdale 2, which is about the size of a footstool, is the first rock the rover has examined in detail at Endeavour. So, researchers stressed, their investigation is still preliminary. They can't yet say for certain that Opportunity has uncovered a long-dead hydrothermal system — but it's a possibility.

Further, this system might be even more exciting than the one Spirit found four years ago. The warm water in that system was likely to have been very acidic, Squyres said. So was a lot of the other water bubbling out of the Martian ground long ago, both near Spirit's site and near Opportunity's site.

But the rocks and soil around Endeavour might be more neutral and thus more benign, researchers said. NASA spacecraft orbiting Mars have gathered compelling evidence that there are clay minerals in the area. And clay minerals don't form in acidic conditions.

"So if there really are clay minerals present, as we suspect there are," Squyres said, "then that points to water with a very different chemistry — water that's more neutral, and conditions that would have been more suitable for life."

A hydrothermal system doesn't necessarily mean flowing water, he added. Hot water vapor may have also moved through the rocks long ago.

And it was long, long ago — likely billions of years, researchers said.

NASA / JPL-Caltech / Cornell / ASU

This rock, informally named "Tisdale 2," was the first rock Opportunity examined in detail on the rim of Endeavour crater. The 12-inch-tall (30-centimeter-tall) rock has textures and composition unlike any rock the rover examined during its first 90 months on Mars. Its characteristics are consistent with the rock being a breccia — a type of rock fusing together broken fragments of older rocks.

The heat to power this system may have come from the impact that created Endeavour, Squyres said. Such a destructive event would have transferred mammoth amounts of heat to the red dirt and rocks.

Just getting started
Researchers hope to flesh out just what's going on at Endeavour over the coming weeks and months. Opportunity, after all, has only just begun studying the giant crater.

"Amazingly, after seven years and eight months, we're embarked on a brand-new mission," said Ray Arvidson, the rover mission's deputy principal investigator at Washington University in St. Louis. [Video: Opportunity's 7 Years of Mars Roving]

Opportunity and Spirit landed on Mars in January 2004, on what was planned to be just a three-month mission to search for signs of past water activity on Mars. Both robots delivered in a big way, finding lots of evidence that the Red Planet was a much wetter, warmer place in the ancient past.

The twin rovers long outlasted their warranties.

Spirit stopped communicating with Earth in March 2010, and NASA pronounced the rover dead this past May. Opportunity, however, is still going strong. It has now covered 20.8 miles (33.5 kilometers) on the Martian surface — more than 30 times its original distance objective.

Opportunity is showing some signs of its advanced age. Mission engineers have been driving the rover backward for the last few years, for example, to distribute the wear more evenly among the rover's gear mechanisms.

But the rover keeps chugging along. And it finally reached Endeavour, which has been its targeted destination since August 2008. The mission team is excited to start studying the crater's environs in detail.

"This has the potential to be the most revealing destination ever explored by Opportunity," said Dave Lavery, program executive for NASA's Mars Exploration Rovers at NASA Headquarters in Washington. "This region is substantially different than anything we've seen before."

You can follow Space.com senior writer Mike Wall on Twitter: @michaeldwall. Follow Space.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

The face of Mars

The Hubble Space Telescope focuses on the full disk of Mars, with a head-on view of a dark feature known as Syrtis Major. Hubble astronomers could make out features as small as 12 miles wide.
(AURA / STSCI / NASA)
ShareBack to slideshow navigation

Red, white and blue planet

Two decades before Pathfinder, the Viking 1 lander sent back America's first pictures from the Martian surface. This 1976 picture shows off the lander's U.S. flag and a Bicentennial logo as well as the planet's landscape.
(NASA)
ShareBack to slideshow navigation

Grand canyon

This is a composite of Viking orbiter images that shows the Valles Marineris canyon system. The entire system measures more than 1,875 miles long and has an average depth of 5 miles.
(NASA)
ShareBack to slideshow navigation

Red rover

A mosaic of eight pictures shows the Pathfinder probe's Sojourner rover just after it rolled off its ramp. At lower right you can see one of the airbags that cushioned Pathfinder's landing on July 4, 1997.
(NASA)
ShareBack to slideshow navigation

Twin Peaks at their peak

The Pathfinder probe focuses on Twin Peaks, two hills of modest height on the Martian horizon. Each peak rises about 100 feet above the surrounding rock-littered terrain.
(NASA)
ShareBack to slideshow navigation

Blue horizon

A Martian sunset reverses the colors you'd expect on Earth: Most of the sky is colored by reddish dust hanging in the atmosphere, but the scattering of light creates a blue halo around the sun itself.
(NASA / JPL)
ShareBack to slideshow navigation

Two-faced Mars

The image at left, captured by a Viking orbiter in the 1970s, sparked speculation that Martians had constructed a facelike monument peering into space. But the sharper image at right, sent back in 1998 by Mars Global Surveyor, spoiled the effect.
(NASA)
ShareBack to slideshow navigation

A monster of a mountain

Mars' highest mountain, an inactive volcano dubbed Olympus Mons, rises as high as three Everests and covers roughly the same area as the state of Arizona. Mars Global Surveyor took this wide-angle view.
(MSSS / NASA)
ShareBack to slideshow navigation

From Mars with love

This valentine from Mars, as seen by Mars Global Surveyor, is actually a pit formed by a collapse within a straight-walled trough known in geological terms as a graben. The pit spans 1.4 miles at its widest point.
(MSSS / NASA)
ShareBack to slideshow navigation

Sandy swirls

An image taken by Mars Global Surveyor shows a section of the northern sand dunes on Mars' surface. The dunes, composed of dark sand grains, encircle the north polar cap.
(JPL / NASA)
ShareBack to slideshow navigation

Curls of clouds

Global Surveyor focuses on a storm system over Mars' north polar region. The north polar ice cap is the white feature at the top center of the frame. Clouds that appear white consist mainly of water ice. Clouds that appear orange or brown contain dust.
(MSSS / NASA)
ShareBack to slideshow navigation

Swiss cheese

Global Surveyor captured images of a frost pattern at Mars' south polar ice cap that looks like Swiss cheese. The south polar cap is the only region on the Red Planet to contain such formations.
(NASA / JPL / Malin Space Science)
ShareBack to slideshow navigation

Purple Planet

A false-color image from the Opportunity rover, released Feb. 9, 2004, accentuates the differences between a green-looking slab of Martian bedrock and orange-looking spheres of rock. Scientists likened the "spherules" to blueberries embedded within and scattered around muffins of bedrock. The spherules are thought to have been created by the percolation of mineral-laden water through the bedrock layers.
(NASA / JPL / Cornell University)
ShareBack to slideshow navigation

Dunes of Mars

A false-color view from NASA's Opportunity rover, released Aug. 6, 2004, shows the dune field at the bottom of Endurance Crater. The bluish tint indicates the presence of hematite-containing spherules ("blueberries") that accumulate on the flat surfaces of the crater floor.
(NASA / JPL / Cornell University)
ShareBack to slideshow navigation

Alien junkyard

The Opportunity rover looks at its own heat shield, which was jettisoned during the spacecraft's descent back in January 2004, on Dec. 22, 2004. The main structure from the heat shield is at left, with additional debris and the scar left by the shield's impact to the right. The shadow of the rover's observation mast is visible in the foreground.
(NASA / JPL)
ShareBack to slideshow navigation

Devil on Mars

This image shows a mini-whirlwind, also known as a dust devil, scooting across the plains inside Gusev Crater on Mars, as seen from the Spirit rover's hillside vantage point on April 18, 2005.
(NASA / JPL)
ShareBack to slideshow navigation

Rub al Khali

The tracks of NASA's Opportunity rover are visible in a panoramic picture of a desolate, sandy stretch of Martian terrain in Meridiani Planum, photographed in May 2005 and released by NASA on July 28. "Rub al Khali" (Arabic for "Empty Quarter") was chosen as the title of this panorama because that is the name of a similarly barren, desolate part of the Saudi Arabian desert on Earth.
(NASA / JPL / Cornell University)
ShareBack to slideshow navigation

Double moons

Taking advantage of extra solar energy collected during the day, NASA's Spirit rover spent a night stargazing, photographing the two moons of Mars as they crossed the night sky. The large bright moon is Phobos; the smaller one to its left is Deimos.
(NASA / JPL / Cornell / Texas A&M)
ShareBack to slideshow navigation

Mars in the round

A 360-degree panorama shows a stretched-out view of NASA's Spirit rover and its surroundings on the summit of Husband Hill, within Mars' Gusev Crater. The imagery for the panorama was acquired in August, and the picture was released on Dec. 5.
(NASA)
ShareBack to slideshow navigation

Fossil delta

Scientifically, perhaps the most important result from use of the Mars Orbiter Camera on NASA's Mars Global Surveyor has been the discovery in November 2003 of a fossil delta located in a crater northeast of Holden Crater.
(NASA / JPL / MSSS)
ShareBack to slideshow navigation

Underneath the ice

This view taken in January 2005 shows sharp detail of a scarp at the head of Chasma Boreale, a large trough cut by erosion into the Martian north polar cap and the layered material beneath the ice cap.
(NASA / JPL / MSSS)
ShareBack to slideshow navigation

Celestial celebration

Controllers at NASA's Jet Propulsion Laboratory in Pasadena, Calif., cheer on Friday after hearing that Mars Reconnaissance Orbiter successfully made it into orbit around the Red Planet.
(Phil McCarten / Reuters)
ShareBack to slideshow navigation

Editor's note:
This image contains graphic content that some viewers may find disturbing.